1. Field of the Invention
The present invention relates to an instrument for removing dental restorations, e.g. a crown restoration, a temporary crown, a post, a core, and a bridge, attached to natural teeth, artificial teeth, etc.
2. Description of Background Art
Conventional instruments for removing dental restorations are disclosed in Japanese Patent Application Unexamined Publication (KOKAI) Numbers [hereinafter referred to as xe2x80x9cJP(A)xe2x80x9d] 8-56960 and 7-100150.
JP(A) 8-56960 discloses a forceps- or pliers-like instrument having a pivot shaft. The instrument has a rod-shaped auxiliary member coaxially connected to the pivot shaft with a universal joint provided therebetween. To remove a dental restoration, slits are made in the dental restoration. Then, the jaws of the instrument are inserted into the slits to grip the dental restoration, and the distal end of the auxiliary member is axially tapped or pulled to thereby remove the dental restoration.
JP(A) 7-100150 discloses an instrument having a pair of levers each bent at the joint between a horizontal portion and a vertical portion in the shape of a 90-degree rotated L. Annular proximal end portions of the levers are pivotably connected together by a connecting stem. The levers have a pair of wedges projecting from the distal ends of the vertical portions so that the wedges face each other. The wedges are tapered toward each other""s distal ends. The horizontal portions are connected at intermediate positions thereof by a rotating bolt so that the two bent levers can be opened or closed through threaded engagement between the rotating bolt and the horizontal portions, thereby allowing the spacing between the opposing ends of the wedges to be enlarged or reduced. To remove a dental restoration from a tooth, outer symmetric surfaces of the joint between the dental restoration and the tooth are cut to form wedge-shaped recesses with a slitter. Then, the wedges are inserted into the recesses, and the rotating bolt is rotated to reduce the spacing between the opposing ends of the wedges, thereby forcing the wedges into the recesses toward the center of the joint. By virtue of the taper formed on the wedges, when forced into the recesses, the wedges produce force acting on the tooth obliquely downward and force acting on the dental restoration obliquely upward. Consequently, the dental restoration is removed from the tooth.
However, the above-described conventional dental restoration removing instruments require that a dental restoration to be removed should be provided with slits (JP (A) 8-56960) or wedge-shaped recesses (JP (A) 7-100150) for engagement with the instrument in advance of the removal of the dental restoration. In other words, it is impossible to remove the dental restoration unless it is drilled or destroyed. Accordingly, a great deal of time is needed to remove the dental restoration, and the patient must bear the pain for an unfavorably long period of time. In addition, it takes the dentist a great deal of labor to remove the dental restoration. With the conventional dental restoration removing instruments, dental restorations once removed cannot be reused, which is unfavorable from the viewpoint of cost. Moreover, both the conventional instruments suffer from the problem that the arrangement of the instruments is completed, and the production cost is undesirably high, and further the operation is complicated.
In view of the above-described circumstances, an object of the present invention is to provide a dental restoration removing instrument free from the above-described problems with the prior art.
To attain the above-described object, the present invention provides a dental restoration removing instrument, e.g. a forceps or a pair of pliers, of the type wherein a pair of jaws at the distal end of the instrument grip an object in response to an operation of closing a pair of handles. The pair of jaws have distal ends that can be wedged into the boundary between a tooth and a dental restoration from both sides thereof. The distal end of each jaw has an angle whereby the tooth can be pushed downward and the dental restoration can be pushed upward. The instrument has an opening angle adjusting device for adjusting the opening angle between the jaws so that the distal ends of the jaws will not bite into the boundary between the tooth and the dental restoration more than a predetermined amount.
The angle is provided at the distal end of each jaw allows the jaws of the instrument to be wedged into the boundary between the tooth and the dental restoration without the need to provide slits or recesses in the dental restoration. Therefore, the instrument can be engaged with the dental restoration without destroying the latter. In addition, the dental restoration can be removed with the instrument without a possibility of undesirably pulling out the tooth together with the dental restoration, and without applying such a force that destroys the tooth or the dental restoration when the object is gripped with the instrument.
Further, because the opening angle of the instrument can be set in conformity to the tooth under treatment by adjusting the opening angle adjusting device, there is no possibility that the jaws will excessively bite into the boundary between the tooth and the dental restoration, causing the tooth or the dental restoration to be damaged.
Preferably, the distal end of each jaw has a wedge-like shape with a predetermined angle with which the distal end of each jaw is wedged into the boundary between the tooth and the dental restoration. The angle is so determined that the distal end of each jaw is disposed perpendicularly to the axis of the tooth.
By virtue of the above-described arrangement, it is possible to insert the distal ends of the jaws into the boundary between the tooth and the dental restoration while wedging the boundary by applying an upward pushing force to the dental restoration without a possibility of undesirably pulling the tooth together with the dental restoration and without applying unnecessary force to the tooth. Accordingly, the distal ends of the jaws can be readily wedged into the boundary between the tooth and the dental restoration without damage to the tooth even if the dental restoration is not provided with slits or recesses for engagement with the distal ends of the jaws.
When the instrument is gripped to remove the dental restoration, force is applied to the tooth from the outer slant portions contacting the tooth. In this case, however, the inclination angle of each outer slant portion causes the force to be applied to the tooth obliquely in a dispersed state from an upper portion at each side of the tooth toward a lower central portion thereof. Therefore, it is unlikely that the tooth, which is not very resistant to force applied vertically, will be damaged. On the other hand, strong force is applied to the dental restoration so as to push it up. Accordingly, the joint portion of the dental restoration is smoothly disengaged from the tooth, and thus the dental restoration is removed from the tooth.
Preferably, the distal end of each jaw has an inner slant portion, a first outer slant portion adapted to contact the boundary between the tooth and the dental restoration, and a second outer slant portion adjacent to the first outer slant portion on a side of the first outer slant portion remote from the boundary. The predetermined angle of the distal end of each jaw is as follows. When the distal ends of the jaws are disposed perpendicularly to the axis of the tooth, the inner slant portion has an inclination angle of about 20xc2x15 degrees with respect to a horizontal plane perpendicular to the axis of the tooth. The first outer slant portion has an inclination angle of about 35xc2x15 degrees with respect to the horizontal plane. The second outer slant portion has an inclination angle of about 1xc2x11 degrees with respect to the horizontal plane.
The opening angle adjusting device may be a screw threaded into one of the pair of handles so that the distal end of the screw extending through the handle can abut on the other of the pair of handles.
With the above-described arrangement, if the extent to which the screw is threaded into the one handle is increased, the distal end of the screw abuts on the other handle at an increased angle of opening between the two handles. Consequently, the distance between the distal ends of the jaws is set large. If the extent to which the screw is threaded into the one handle is reduced, the distal end of the screw abuts on the other handle at a reduced angle of opening between the two handles. Consequently, the distance between the distal ends of the jaws is set small. Thus, the opening angle can be adjusted according to the extent to which the screw is threaded into the one handle. Accordingly, the instrument is simplified in arrangement and becomes easy to produce.
The handles may have an inclination angle of about 40 degrees with respect to the jaws when placed horizontally, whereby the distal ends of the jaws can be wedged into the boundary between a molar or the like and a dental restoration from both sides thereof.
In regard to a dental restoration removing instrument for molars, the handles are formed so as to have an inclination angle of about 35 to 40 degrees with respect to the jaws when placed horizontally, as stated above. Accordingly, it is easy to insert the instrument into the patient""s mouth as far as the molar under treatment while keeping the instrument from touching any of the upper and lower front teeth and then wedge the distal ends of the jaws into the boundary between the molar under treatment and the dental restoration at right angles to the axis of the molar.
Preferably, the jaws each have a constriction formed at the distal end thereof.
In a case where the jaws of the instrument cannot be disposed at right angles to the buccal and lingual sides of the tooth under treatment when the jaws are wedged into the boundary between the tooth and the dental restoration, it may be necessary to rotate the jaws with respect to the axis of the tooth under treatment and to use the instrument in this position. In such a case, because the constriction is formed at the distal end of each jaw, there is no possibility of the jaw contacting a tooth adjacent to the tooth under treatment and causing interference with the operation. Therefore, the instrument provides excellent operability.
The dental restoration removing instrument may be arranged such that the distal ends of the jaws each have a wedge-like shape with a predetermined angle with which the distal end of each jaw is wedged into the boundary between the tooth and the dental restoration from both sides thereof, and the angle is so determined that the distal end of each jaw is disposed perpendicularly to an imaginary line connecting both sides of the boundary.
In the above-described arrangement, the distal ends of the jaws each have an inner slant portion, a first outer slant portion adapted to contact the boundary between the tooth and the dental restoration, and a second outer slant portion adjacent to the first outer slant portion on a side of the first outer slant portion remote from the boundary. The predetermined angle of the distal end of each jaw is as follows. When the distal ends of the jaws are disposed perpendicularly to the imaginary line connecting both sides of the boundary, the inner slant portion has an inclination angle of about 20xc2x15 degrees with respect to a horizontal plane perpendicular to the axis of the tooth. The first outer slant portion has an inclination angle of about 35xc2x15 degrees with respect to the horizontal plane. The second outer slant portion has an inclination angle of about 1xc2x11 degrees with respect to the horizontal plane.
In another aspect of the present invention, a dental restoration removing instrument is provided, configured in the manner of a forceps or a pair of pliers, that includes a pair of pivoted handles, and a pair of jaws at a distal end of each of the pair of handles configured to grip an object in response to an operation of closing the pair of handles. The pair of jaws includes distal ends that can be wedged into a boundary between a tooth and a dental restoration from both sides thereof, the distal ends each having an angle whereby the tooth can be pushed downwardly and the dental restoration can be pushed upwardly. Additionally, the distal ends of the jaws may each have a wedge-shape with a predetermined angle with which the distal end of each jaw is wedged into the boundary between the tooth and the dental restoration, with the angle being determined such that the distal end of each jaw is disposed perpendicularly to an axis of the tooth.
According to another aspect of the present invention, the distal ends of the jaws may each have an inner slant portion, a first outer slant portion configured to contact the boundary between the tooth and the dental restoration, and a second outer slant portion adjacent to the first outer slant portion on a side of the first outer slant portion remote from the boundary. The predetermined angle of the distal end of each jaw is configured such that, when the distal ends of the jaws are disposed perpendicularly to the axis of the tooth, the inner slant portion has an inclination angle of about 20xc2x15 degrees with respect to a horizontal plane perpendicular to the axis of the tooth, and the first outer slant portion has an inclination angle of about 35xc2x15 degrees with respect to the horizontal plane. Furthermore, the second outer slant portion has an inclination angle of about 1xc2x11 degrees with respect to the horizontal plane.
In a further aspect of the dental restoration removing instrument according to the present invention, an opening angle adjusting device may be provided that adjusts an opening angle between the jaws so that the distal ends of the jaws will not bite into the boundary between the tooth and the dental restoration more than a predetermined extent. Alternatively, the opening angle adjusting device may include a screw threaded into one of the pair of handles so that a distal end of the screw extending through the handle can abut on the other of the pair of handles.
In other aspects of the dental restoration removing instrument according to the present invention, the handles may have an inclination angle of about 35 to 45 degrees with respect to the jaws when placed horizontally, whereby the distal ends of the jaws can be wedged into a boundary between a molar and a dental restoration. Additionally, the jaws may each have a constriction formed at the distal end thereof. Moreover, the distal ends of the jaws may also each have a wedge-shape with a predetermined angle with which the distal end of each jaw is wedged into the boundary between the tooth and the dental restoration from both sides thereof, the angle being determined such that the distal end of each jaw is disposed perpendicularly to an imaginary line connecting both sides of the boundary.
In another aspect of the present invention, the dental restoration removing instrument according to the present invention may also include a first outer slant portion configured to contact the boundary between the tooth and the dental restoration, and a second outer slant portion adjacent to the first outer slant portion on a side of the first outer slant portion remote from the boundary. The predetermined angle of the distal end of each jaw may be configured such that, when the distal ends of the jaws are disposed perpendicularly to the imaginary line connecting both sides of the boundary, the inner slant portion has an inclination angle of about 20xc2x15 degrees with respect to a horizontal plane perpendicular to the axis of the tooth, the first outer slant portion has an inclination angle of about 35xc2x15 degrees with respect to the horizontal plane, and further the second outer slant portion has an inclination angle of about 1xc2x11 degrees with respect to the horizontal plane.
According to another aspect of the present invention, a method of removing a dental restoration is provided that includes providing an instrument having a pair of pivoted handles and a pair of jaws at a distal end of each of the pair of handles, the pair of jaws including distal ends that can be wedged into a boundary between a tooth and a dental restoration from opposite sides thereof, and the distal ends each having an angle whereby the tooth can be pushed downwardly and the dental restoration can be pushed upwardly. The method also includes positioning the distal ends of the jaws at a boundary of a dental restoration to be removed and a tooth covered by the dental restoration, adjusting a position of the distal ends to be firmly engaged with the boundary and wedged thereinto, and repeatedly gripping the handles to apply instantaneous force to the boundary and to apply a downward pushing force on the tooth and an upward pushing force on the dental restoration to cause a joint portion of the dental restoration to disengage from the tooth.
In another aspect of the present invention, the method of removing a dental restoration may also include providing the distal ends of the jaws with a wedge-shape having a predetermined angle with which the distal end of each jaw is wedged into the boundary between the tooth and the dental restoration, the angle being determined such that the distal end of each jaw is disposed perpendicularly to an axis of the tooth.
In a further aspect of the present invention, the method may further include providing the distal ends of the jaws with an inner slant portion, a first outer slant portion configured to contact the boundary between the tooth and the dental restoration, and a second outer slant portion adjacent to the first outer slant portion on a side of the first outer slant portion remote from the boundary. The method further includes configuring the predetermined angle of the distal end of each jaw such that, when the distal ends of the jaws are disposed perpendicularly to the axis of the tooth, the inner slant portion has an inclination angle of about 20xc2x15 degrees with respect to a horizontal plane perpendicular to the axis of the tooth, and the first outer slant portion has an inclination angle of about 35xc2x15 degrees with respect to the horizontal plane, and further the second outer slant portion has an inclination angle of about 1xc2x11 degrees with respect to the horizontal plane.
According to another aspect of the present invention, the method of removing a dental restoration may also include providing an opening angle adjusting device that adjusts an opening angle between the jaws so that the distal ends of the jaws will not bite into the boundary between the tooth and the dental restoration more than a predetermined extent. Additionally, the method may include providing the opening angle adjusting device with a screw threadable into one of the pair of handles, and adjusting the opening angle by threading the screw into the one of the pair of handles so that a distal end of the screw extending through the handle abuts on the other of the pair of handles to thereby limit the opening angle.
In further aspects of the present invention, the method of removing a dental restoration may further include providing the handles with an inclination angle of about 35 to 45 degrees with respect to the jaws when placed horizontally, whereby the distal ends of the jaws can be wedged into a boundary between a molar and a dental restoration, and providing each the jaw with a constriction formed at the distal end thereof. Additionally, the method of removing a dental restoration may further include providing the distal ends of each the jaw with a wedge-shape having a predetermined angle with which the distal end of each jaw is wedged into the boundary between the tooth and the dental restoration from both sides thereof, the angle being determined such that the distal end of each jaw is disposed perpendicularly to an imaginary line connecting both sides of the boundary.
According to a still further aspect of the present invention, the method of removing a dental restoration may further include providing the distal ends of each the jaws with an inner slant portion, a first outer slant portion configured to contact the boundary between the tooth and the dental restoration, and a second outer slant portion adjacent to the first outer slant portion on a side of the first outer slant portion remote from the boundary. The method further includes configuring the predetermined angle of the distal end of each jaw such that, when the distal ends of the jaws are disposed perpendicularly to the imaginary line connecting both sides of the boundary, the inner slant portion has an inclination angle of about 20xc2x15 degrees with respect to a horizontal plane perpendicular to the axis of the tooth, and the first outer slant portion has an inclination angle of about 35xc2x15 degrees with respect to the horizontal plane, and further the second outer slant portion has an inclination angle of about 1xc2x11 degrees with respect to the horizontal plane.